280z Electrical Issues

[Pac_Man]

Hi everyone,

 

I've been getting some advice in the build thread I've got going but figured this would be the better place to chase after the issues I'm having since it's more technical and a better setting to get pointers of what to look for.

 

So the background:

 

1976 280z with an 11/75 build date if it matters. Effectively stock, save for a few minor things and an L28ET.

 

A couple issues that are electrical-related:

 

1) The system does not seem to be charging. Charge light was off with the car running. I ran the engine for a bit and noticed the fuel pump kept getting louder and the engine running rougher so I turned it off and found that the battery read ~11.3 volts. Checked the wiring at the alternator and it checked out so I started the car again and tested voltage at the battery and the alternator positive post. Both read ~11.3 volts. Had the alternator and battery both tested at O'reilly on their machine and it said it checks out, though I know that isn't a final judgement on whether or not an alternator is really working properly or not. By that point I had assumed it was the voltage regulator. Replacements aren't easy to get and they're either expensive or the shipping costs more than the unit. By the time that would all be said and done I figured I would be better off buying an internally regulated 280zx alternator.

 

The alternator is a reman. unit from O'reilly that was on the old engine before without issue. Is there something else I could be missing here? I got a longer bolt/screw for the "E"/ground post of the alternator since the old one couldn't hold the wire and the capacitor at the same time. Is there some chance that the one I used isn't allowing the alternator to get a proper ground? I've also read things about how if the battery isn't charged enough the alternator won't charge, but I doubt that was the case since it seemed that the battery was at good voltage but gradually draining.

 

I'm tempted to pull the trigger on a new internally regulated alternator and throw it in, but I would rather have someone point out what I can't seem to see is wrong before I spend the money on it.

 

 

2) The tachometer and oil/water gauge are not working. I know I have oil pressure as I verified that before starting the engine. The sending unit is new and I know it's getting oil. The stock tachometer coil signal wire is hooked up and I verified it at the resistor under the passenger side of the dash. Also verified continuity and resistance in the resistor.

 

As far as I can tell, the gauges are getting the signal, they just aren't being powered. The lights do come on but after reviewing the wiring diagram those seem to be on a separate circuit anyway. 

 

According to another forum member, the 4th fuse down on the left side of the fuse panel provides voltage to the gauges. The fuse is fine and has continuity, though I don't get voltage on either side of the fuse. After checking where the fuse gets power from, it seems to be hooked into switched voltage from a black and white wire that is spliced in at multiple points throughout the car. Here's where it gets interesting, though. The fuse that provides power to the voltage/fuel gauge also appears to be fed by that wire, and I know my voltage/fuel gauge is working.

 

I feel like I'm going crazy trying to track down the cause of the issue since every lead (no pun intended) I find ends up in me thinking that it should be working fine.

 

 

Any advice is appreciated as always. Like I always say, HybridZ is the place I turn to when all my efforts seem to be getting me nowhere.

 

- Pac Man

[NewZed]

On 1 - you didn't say anything about rewiring to use an internally regulated alternator.  It's not just a bolt-in and go swap.  

 

On 2 - have you read page BE-42?  At least that's the page in the 1976 FSM.  The 1975 version online doesn't seem to have a BE chapter.  No signs of any meter measurements either.  Take the gauge out and measure at the plug if you can't find the source wire.

[Pac_Man]

Oh I know it isn't just a direct bolt-in, but I know that it's a common swap with a lot of information on it. I'm confident that I could do it easily.

 

As for the BE section of the FSM, I didn't really find anything in there. I have an understanding of how the gauges read, it's just that I'm almost certain they aren't getting power. The fuses for the gauges get fed 12v+ switched power from the ignition switch in the On/Start positions so I guess my first step is to check and see if the fuse box wire gets voltage when the key is turned to On.

[NewZed]

Missed the part about "you were tempted".  Thought you already did it.  There's a whole long procedure for testing the external regulator in the Engine Electrical chapter.  But, it sounds like your L wire has just lost it's connection.  I think that is described in FSM also.  The simplest of checks is to just turn on the key and check for battery voltage at the T plug on the alternator.

 

When working on electrical stuff, your first action is always to check that power is getting to where it's supposed to be getting.  Once you actually use a meter for more than 5 minutes and either confirm power, or confirm no power, you'll never post again about "maybe I should check for power".  It will be incomprehensible to not use the meter first.  Some people carry meters in their car.

[cgsheen]

Have you unbolted your fuse block and looked at the back side?  The B/W from the IGN switch feeds two fuses (3rd and 4th from the top, left side).

 

3rd:  Marked "F" - Green wire out to:  Voltage Regulator, Water Temp Relay (except CA), "Check" Connector, A/T something, Catalyzer Hold Relay (CA), Bunch of Cat related stuff for CA models.

 

4th:  Marked "Int" (?) - Blue wire out to: Hazard switch, Fuel Warning lamp, Ignition Interlock, Coolant Temp & Oil Pressure Gauge, Auto Trans Kickdown Switch, Interlock Relay.

 

So...  You need Battery Voltage on the B/W that feeds the fuse block.  Check the back for heat / melting.  Trace the B/W back to the IGN Switch to see why there's no voltage.  Check and make sure it's not melted down in the dash harness.  I'd want to know why there's no voltage at the fuse block.

 

(The B/W will branch off various ways - From the IGN Switch it also runs over to the passenger side through the dash, goes up the passenger fender well, across the radiator core support, to the coil location...)

[Pac_Man]

Hi cgsheen,

 

I did unbolt the fuse panel and looked at the back. Nothing unusual there. After reviewing a diagram I have, power going to the fuse block passes through the ignition relay before continuing to the fuse panel. Unless this diagram I have is incorrect, I concluded that is the reason why I was not getting voltage to that wire as the relay is disconnected. I had absolutely no issues before and the only changes I made were removing the old EFI harness and disconnecting most of the ignition harness.

 

I hooked up a temporary connection to a known 12v switched source and everything works normally with that.